GB944540A - - Google Patents

Abstract

944,540. Electrolytic capacitors. TELEGRAPH CONDENSER CO. Ltd. April 24, 1962 [June 19, 1961], No. 15572/62. Drawings to Specification. Heading H1M. A method of manufacturing a solid electrolyte capacitor comprises the steps of forming a dielectric film upon the surface of a film forming electrode (which constitutes the anode of the capacitor), coating the film with a solution comprising an organic charge-transfer complex compound having a resistivity in the dry state and at room temperatures not exceeding 1000 ohm-cm., removing the solvent from the solution so as to leave a solid layer of the said organic compound, which constitutes the cathode layer, on the dielectric film, and covering the layer of organic compound with an electrically conductive material. By a chargetransfer complex is meant the complex resulting from the interaction of two molecules in the electron donor sense, one molecule acting as an electron donor, the other as an electron acceptor. Particularly useful charge-transfer complexes are perylene-bromine and perylene-iodine complexes, which have low resistivities (approx. 8 ohm-em. at room temperature), but the Specification lists a number of other suitable complexes whose resistivities are in the appropriate range. Suitable solvents are hydrocarbons, alcohols, chloroform and acetonitrile, which have boiling points below 125‹ C. A particularly suitable anode material would be a porous tantalum pellet with an anode film provided by formation by electrolysis in a phosphoric acid electrolyte, but the Specification also refers to other film forming metals-aluminium, niobium and titanium, and other structures such as foil and wire. The contact cathode electrode may be silver on a foundation layer of graphite, and the entire unit may be housed in a metallic can.